The night sky over one of the world's oldest known man-made structures. Göbekli Tepe is an archaeological site in the Southeastern Anatolia Region of Turkey, near the town of Şanlıurfa. The hill includes two phases of ritual use dating back to the 10th-8th millennium BC. It included circles of over 200 massive T-shaped stone pillars were erected. Each pillar is up to 6 m high and 20 tons. The function of the structures believed to be early neolithic sanctuaries. Tunc Tezel